Fine autoradiographical study on scale morphogenesis in the regenerating tail of lizards.

Regenerating scales in lizards originate as pockets in the epidermis instead of epidermal elevations as during embryo development. The morphogenesis of scales in the regenerating tail of the lizards. Anolis and Lamphropholis was studied after peritoneal injection of 3H-thymidine. The tracer was localized in the forming epidermis after progressive post-injection times, by means of autoradiography on plastic sections. After 4-5 hours post-injection of 3H-thymidine, the radioactivity was localized in the basal layer. After 2 to 4 days post-injection labelled cells were seen in the basal and intermediate spinosus layers but not in the uppermost keratinizing layers. Labelled cells were seen in the differentiating cornifying layers (pre-beta and pre-alpha) 6-8 days post-injection. At 12-14 days post-injection almost no radioactivity was seen in the basal layer or in the living part of the epidermis. A few labelled cells were present in the dense keratinizing layers of the sloughing wound and interscale lacunar layers. This study shows that scale formation and morphogenesis in the regenerating tail is brought about by a localized cell proliferation along the regenerating epidermis. In the forming scales the percentage of labelled cells in the distal side (future dorsal part of the new scale) is much higher than in the proximal side (the future ventral side of the scale), so that overlapped scales are generated.